I frequently run in to libertarians who, when pushed, would agree to keep crack cocaine illegal but legalize pot. But you cannot draw that line on the libertarian principle of do whatever you want as long as you don't punch someone or steal their money, even though these libertarians will try to argue from that sort of principle to justify legalized marijuana.
That type of 'libertarian' is really a conservative who draws the line in a different spot than another conservative. There's solid, conservative arguments on both sides of that issue and I wish they were made more respectfully, but the 'principle' argument of libertarianism doesn't work because it does not admit permissible lines short of punching or stealing.
Generally I agree with what you wrote but holding liberarians to some "pure" standard is as unreasonable as holding a conservative some "pure" black and white standard. The first problem of course is that no one will ever agree on what that standard should, be be they libertarians or conservatives.
Not really, unless you hold that absolutes apply in all circumstances. Punching/stealing are simply metaphors, and limited government does not mean no government---it just means government sticks to its limited scope. If the state can make a compelling case that power needs to be exercised in a certain area, let them make that case to the people, and have the people vote to give them that power, rather than assume the power by fiat or subterfuge.
Nonsense. The "principle" argument works perfectly well when the line is drawn at "assault" -- which does not require actual injury. I may not demonstrate my marksmanship skills by shooting down flies buzzing around you with a pistol, because that is an assault even if I succeed at hitting the flies and do you no harm whatsoever.
On that basis, one may maintained a principled position that prohibition against drugs that are reasonably likely to produce "berzerker" reactions that endanger bystanders (e.g. crack and PCP, but not pot) is justified.